Hi Tony.
What make (and model) is the speaker?
Can you describe the fault? (Is it jammed rigid, rubber surround perished, distorting, smoking, fishing, swearing or just plain doing nothing?)

These things affect wether or not it's worth repairing, where to send to for repair or to get parts to fix it yourself. Depending on the answers to the above it may well be worth simply replacing with new equivalents.

I'm sure you have but I'll ask anyway......
How do you know the crossover isn't the problem?